Statistical apparatus



March 19, 1940 HUMPHR|E$ 2,194,072

STATISTICAL APPARATUS Filed Dec. 16, 1936 3 Sheets-Sheet 1 FIG].

March 19, 1940. H. E. HUMPHRIES 2,194,072

STATISTI CAL APPARATUS Filed Dec. 16, 1936 s Sheets-Sheet 2 ly- I &% 4Xrrrn Patented Mar. 19, 1940 s t, Fries STATISTICAL APPARATUS Horace Edgar Humphries, Blackheath, London, England, assignor to Siemens Brothers & Company Limited, London, England Application December 16, 1936, Serial No. 116,065 I I In Great Britain January 16,1936

15 Claims. .(ci. irec)" The present invention relates to electrical statistical apparatus and has in view the production of a statistical apparatus for use in connection with a plurality of units of apparatus. The purpose of the statistical apparatus of the invention is to record, and it may be to indicate, the percentage occupancy, during a chosen period of time, of the said units of apparatus.

Ihe term percentage occupancy during a period is understood to relate, not to the condition during particular moments nor to the condition of particular units, but to the average condition of all the units considered as a single aggregation during the whole of a period. Thus, if each of the units is occupied during the whole period, the percentage occupancy during the period is one hundred: if none of the units is occupied during all of the period, the percentage occupancy during the period is zero; and, if half of the units are occupied during the whole of the period or all are occupied during half of the period, the percentage occupancy during the period is fifty.

An example of the sort of unit of apparatus, and of the users thereof, is afforded by a telephone system; and aparticularly good example,

i by a trunk telephone system. In a trunk telephone system, a number of trunk lines which extend between two towns may be regarded as the units of apparatus, and subscribers upon whose behalf operators serve those trunks may be regarded as the users. On account of the cost of such trunk lines it is undesirable to provide more of them than are necessary and if it be permissible to introduce a slight delay in the supplying of the demands of the users, it may even be feasible to providepslightly less than are needed to deal with the whole of the simultaneous demands which may momentarily occur. In order that a satisfactory service may be given, that is that the delay in supplying any particu lar demand may not be too great, it is necessary for the authority to have suitableknowledge of. the conditions, that is of the percentage occu' pancy, of the trunks during suitable periods.

The statistical apparatus of the present invention, which hereinafter will be referred to merely as the statistical apparatus, permits, and is designed to permit, the percentage occupancy for a period to become known'and to be presented in a readily understood form, preferably directly as a percentage.

The statistical apparatus, to thisend,-takes repeated momentary .glances at the units of apparatus in turn and sees the condition, occupied or unoccupied, of the units as they are during theseglances. It takes note of those units which, it sees vto .begoccupied and when it has taken note of a certain number it causes a rec rd tobe made on a, suitablerecording device of -1% occupancy. I 5 For the sake ofv example let the period be supposed to beone hour, then thehour may be re? garded as consisting of. one hundred divisions of thirty-six seconds each. Let the statistical apparatus be supposed to take two glances in one second, then the number of glances that it takes during one. division of thirty-six seconds will be seventy-twd- Let it be supposed that it sees that all the units are occupied during the first division of thirty-six seconds, that is at the first seventytwo glances, then the number of which it will take note during that division will be seventytwo and at the end of that division it, will cause a record of one to be made for the first division of thirty-six seconds, that is of one hundredth of an hour. It is easy to see that, if during the remaining ninety-nine divisions of thirty-six seconds, the condition, of total occupancy persists, the statistical apparatus will cause a record of a further ninety-nine to be made, that is, for the'hour, a record of one hundred will be made representing 100% occupancy. It is also easy to see that, if during fifty of the remaining ninety-nine divisions of thirty-six seconds the statistical apparatus sees a condition of inoccupancy, it will cause norecord to be made in respect of those divisions but will cause a record to be made in respect of the forty-nine divisions in which it had noted seventy-two conditions of occupancy, that is, for the hour,v a record of fifty.-(forty-nine plus the first one considered) will be made representing 50% occupancy.

It is highly improbable however that the statistical apparatus would see the conditions of occupancy and inoccupancy evenly distributed but it will be appreciated that a total of 7200 glances will be taken during the hour and that whenever a total of '72conditions of occupancy have been'observed a record of one per cent 00- cupa'ncy will be made. Thus at the end of the hour 1% may have been recorded a maximum of one hundred times (representing 100% occupan'cy), or a smaller number of times if the occupancy is less. The number of times 1% will he recorded is, of course, proportionate to the total number of conditions of occupancy 011- served during the hour. It is also not contemplated that there willbe 7 units f ap a atus in a group to be observed and consequently it is arranged that the units of apparatus are. ob-

served repeatedly in cycles during each division.

The invention may be carried out by the association of a timing device, a serial switching device, and a recording device. The timing device is conveniently in the form of a pair of interacting relays operating in a precise time cycle, for example, twice a second, which effect the change of connections of a number of transfer condensers. The condensers are alternately connected in parallel to be charged and in series with a source of power for discharge into a reservoir condenser. When the combined voltages of the reservoir condenser and the source of power reach the striking voltage of a gas discharge tube associated with the reservoir condenser, the tube breaks down and a relay connected in series with the tube is operated. The transfer condensers and the reservoir condenser have associated with them resistances for the control of the charging current. For the purpose of the present invention the charging circuit of the transfer condensers is not closed at each cycle of operation of the interacting relays but is closed only when an occupied unit of apparatus has been observed, the closure being made by a discriminating relay. The relay in the tube circuit when operated brings about an operation of the recording device to record a unit of occupancy.

The serial switching device preferably consists of a number of relays operating in a cycle. Their function is to connect up each of the units of apparatus in succession to the discriminating relay and they are operated by pulses of current delivered by the interacting relays of the timing device.

It is a feature of the serial switching device that the relays comprising it are released by opening their circuits thereby ensuring that they release promptly. When relays are operated and released sequentially by impulses with short intervals between them, as is the case in this invention this feature is of some importance.

The recording device may be a counting mechanism such as that used for metering calls in a telephone system.

Provision may be made for varying the number of units of apparatus to be observed by the statistical apparatus by arrangements whereby the discriminating relay is only connected to those units the condition of which is to be observed.

For the purpose of enabling observations to be readily made in a number of groups of apparatus units the apparatus units may be connected to contacts in the bank of a stepping switch which may be caused by a suitable key operation to set itself in any desired contact position the wipers of the switch being connected to the discriminating relay over serially arranged contacts of the serial switching relays. Where the number of apparatus units in a group is less than the maximum number provided for by the statistical apparatus, more than one group may be connected in any contact position of the switch provided the total number does not exceed the total number provided for by the statistical apparatus.

However, observation of a group of apparatus units greater in number than that provided for by the statistical apparatus may be made by means of additional apparatus, hereinafter referred to as an expansion unit, which may readily be associated with the primary apparatus for the purpose. The expansion unit provides for the simultaneous operation of a number of apparatus units and contains as many discriminating relays as there are outlets to be observed simultaneously. The discriminating relay of the primary apparatus permanently operated and the charging circuit for the transfer condensers controlled by the discriminating relays of the expansion unit. These control parallel circuits, any one of which will pass current equal to that fraction of the total charging current represented by the reciprocal of the number of outlets to be simultaneously observed.

Cal brating arrangements for adjusting the charging current of the transfer condensers may be embodied in the primary apparatus and c 1- pension unit.

A. specific embodiment of the invention will now be described by way of example with reference to accompanying drawings. The drawings show in F 1 and 2 a angements for determining the percentage occupancy over a given period of a number of outlets, up to seven in the present example, irom a group of automatic telephone selecting switches. The outlets may outlets to junctions or trunks leading to another exchange.

3 shows an expansion unit which may be employed with the arrangements of Fig. 2 to enable 9, larger number of outlets to be tested, in the present example up to 21 outlets.

The arrangements shown in Figs. 1 and will first be described. The outlets, the percentage occupancy of which is to be determined over a given period, for example one hour, are connected to corresponding contact positions in the banks of an access switch the relevant wipers of which are designated i, 2 An eighth wiper serves as a test wiper to cause the switch to assume a marked position, a marking being applied to the test bank consequent on the throwing of a key K relevant to the outlet group to be observed. the marked contact in the test bank corresponding in position to the contact positions of the outlets with which the k y is associated. The access switch magnet is do ated 33M and its test relay T. When the outlet is occupied, earth is applied to a wire connected to the associated Contact in one of the banks of the access switch. The key K besides 1 larking the test bank completes a circuit for the switch magnet DM and applies markings as required to designate the first and last outlets of a group to be observed. These latter markings are only required when the group commences at an outlet other than that connected to the bank of wiper l or finishes at an outlet other than that connected to the bank of wiper '1'. It is not necessary that the same contact position should serve only one group of outlets. For instance a number of outlet groups with a total number of outlets not exceeding K may be connected in one contact position of the access switch. In such a case the difierent keys K associated with the several groups will mark the same contact in the test bank engaged by wiper 8 but notice will only be taken of the outlets associated with the operated key.

The time measuring device comprises the relays B, C, D, E, condensers QA-QD and associated series connected resistances and a gas dis charge tube DT. OR is a recording device which may be of the form usually employed as a subscribers or statistical meter.

The step-by-step switching device for observing the several outlets in turn comprises the relays U-Z, ZA and Z13. A is a starting relay, and J the discriminating relay which determines whether an observed outlet occupied or not.

Consideration will first be given to the time iii) measuring device. When a key such as K is thrown, earth is connected over its lower righthand contacts and contacts ti and dm to magnet DM. At the same time earth is connected over the upper right-hand contacts of the key to mark in the test bank of the access switchthe group of outlets to be tested for occupancy. Mag net DM operates and steps the access switch by self interruption of the magnet circuit at contact dm until the marked contact is reached. Thereupon relay T operates, opens the magnet circuit thereby stopping the switch and closes a circuit over its front contact tl, back contacts 03 and (13 for relay A. Relay A operates and locks up over its make-before-break contact a3, contacts e2, t! and key K. Contact al closes a circuit for a slow releasing relay B, contact a2 connects winding (I) of relay J to a chain of contacts of the relay switching device and contact a4 removes a short-circuit from condenser QD. Relay B operates and at its contact bl closes a circuit for winding (I) of slow releasing relay C. Relay C operates slowly, short-circuits relay B at'contact cl and at contacts 02 short-circuits a resistance in its own operating path. Contact 03 changing over produces no efiect on relay A as this relay is held independently of contact 03 over contact 0.3. As a result of the short-circuit over contact cl, relay B releases slowly and when contact bl opens relay C commences to release. When release of relay C is completed, relay B reoperates and the cycle of operation and release of relays B and C re-commences. It is arranged that this cycle takes place in half a second so that two complete cycles are gone through in each second.

Each time relay B operates charging circuits are prepared for condensers QA, QB. and QC in parallel. These circuits extend from earth over contacts al and cl, and b2 for condenser QA, b3 for condenser QB, M for condenser QC, the other sides of the condensers being connected over resistances to contact 71 as follows: condenser QA direct, QB over contact b5 and QC over contact 195. The charging circuit is only completed if relay J is operated and in such a case negative battery is connected over the calibrating resistance CR and the common series resistance SR. If contact jl is closed, the condensers QA, QB and QC are charged in parallel and are then disconnected consequent on the operation of relay C. Each time relay B releases the condensers QA, QB and QC are connected in series to deliver a charge, if they have been previously charged, to the reservoir condenser QD, the circuit for charging condenser QD being from earth over contacts al, bl, resistance and condenser QA, contact b2, resistance and condenser QB, contact b3, resistance and condenser QC, contact 114, resistance YD, condenser QD, thence to battery over contact 02 and winding l of relay C in parallel with a resistance. The battery assists the transfer condensers in charging the reservoir condenser and the latter receives a small charge. Repeated charging and discharging of the transfer condensers will eventually bring the potential of the reservoir condenser to a value such that with the potential of the charging battery in series with it the discharge tube will strike.

It may here be noted that a lamp L is connected in parallel with the tube DT. This lamp is so mounted as to illuminate the tube while the apparatus is in use. It has been found that if the discharge tube has been idle for some time in the dark, the striking potential required at the first impulse is slightly higher than that required for subsequent impulses and this variation of striking potential constitutes a source of error in the record obtained. The effect of the light from the lamp L on the discharge tube is thought to be to maintain constant the ionisation of the gas in the tube and so cause it to strike always at the same potential. I

The discharge circuit for condenser QD is from earth over contacts al, bl, condenser QD, resistance YD, tube DT, relay D to battery. Relay D operates in this circuit and-being a very fast operating relay closes its contact dl before relay E has time to operate. A circuit for relay E is now closed independently of the discharge tube which is extinguished consequent on the short circuit imposed over contacts al and dl. Relay E operates and holds over contact el. Contact 62 releases relay A and holds relay C by means of its winding (II) to prevent its commencing to release immediately and contact e3 completes a circuit for the receiver OR and lights lamp ORL. Relay A falls back and relays D and E release im mediately. The circuit of winding (II) of relay C is opened and that relay commences to release. When release is complete, contact 03 is restored and relay A thereupon re-operates and starts the inter-action of relays B and C once more. During the release of relay A relay J is de-energised thereby preventing any further charging of the transfer condensers and the condenser QD is fully discharged over contact a4. Relay J is only operated when an occupied outlet is observed by the relay switching device and the discharge tube is only struck at such intervals as will cause relay E to operate to indicate 1% ocfore relay C operates winding- '(I) of relay J is connected over contact :12 and back contacts! of the relays UZ to wiper l and an observation is made of the first outlet of the group. When relay'C operates a circuit is completed from earth over key K, contacts tl, c3, M, 201 2, 22, g2, :02, m2, 112, winding (I) of relay U, contacts 03, w3, :03, g3, 23, act, relay ZB, resistance to battery. Relays U and ZB operate. Contact ul disconnects relay J- from wiper l and connects it to wiper 2 for the purpose of observing the second outlet and contact u2 prepares a circuit over winding (II) of relay V. Contact a l opens to prevent operation of relay W on the release of relay C. When relay C releases, relay U continues to hold and relay V operates in the following circuit for winding II: earth over the back contact 03', contact 72, winding (II) of relay V, contact 2L2, winding (I) of relay U, contacts v3, 103, $3, 113, 23, cal, relay ZB to battery. Contact cl prepares for observing outlet 3, contact 122 prepares a holding circuit for relay V and opens a point in the original operating circuit for relay U, contact 223 prepares an operating circuitfo-r relay W and connects the winding I of relay V in series with the circuit for winding II of relay V by removing the short-circuit for the winding at the back contact of 123, and contact o t opens to prevent operation of relay X in parallel with relay V after operation of relay W. On the re-operation of relay C relay U is released due to the disconnection of its winding (I) at back contacts 03 and v2 and relay V is held operated over its winding I. Release of relay U completes the circuit for observing the third outlet. When relay C falls back again a circuit is now completed for relay W which circuit includes contact in winding II of relay W, contact o3, winding I of relay V, contacts 103, m3, y3, 23, cal, relay ZB to battery. Upon operating, winding I of relay W is included in series with winding II or" the relay, due to the removal of the short circuit of contact wt. On the next reoperation of relay C, relay V is released and re lay W is held operated over contact 202 and winding I. Each operation of relay C effects the operation of the succ eding relay in the chain until on the 6th operation of relay C relay Y releases the seventh outlet is observed. The seventh operation of relay C releases relay Z and holds relay EA and the circuit for observing the first outlet is completed. The following release of relay C releases relays EA and ZB and restores the relay chain [or the re-operation of relay U whereupon the above cycle of operations recoinmences. Thus are the outlets observed repeatedly throughout a predetermined interval of time.

During the above described operation relay ZB has remained operated. Contacts chi and 2172 against irregular operation when relay R is operated and contact 2123 disconnects battery from the wires for marking the commencement of a group of outlets under observation should the first not be connected to the bank of wiper B.

Each time an observed outlet is found to be occupied relay J operates, and, as has previously been pointed out, closes a charging circuit for the transfer condensers; accordingly a certain number of operations of relay J will cause the transfer condensers to raise the storage con denser to a potential sufiicient to strike the discharge tube, and it will be seen that the number of times which the tube strikes during any interval of time will be proportionate to the total number of operations of the relay during that in terval. Therefore if during one such interval the tube strikes times and during another interval of equal length it strikes 50 times it is immediately apparent that the occupancy of the outlets during the latter interval is only 50 that of the former. If it is known that during the former interval all of the outlets were continuously occupied (i. e., each observation during the interval found the outlet observed to be occupied) it follows that the percentage occupancy during any interval of equal length may be determined simply by counting the number of times the discharge tube strikes during that interval. For the purpose of adjusting the apparatus sothat over any desired period of time the tube will strike 100 times if every observation finds the outlet observed to be occupied, the calibrating resistance CR is provided; this resistance controls the potential to which the transfer condensers are charged upon each operation of relay J, and thereby determines the number of operations of the relay which will be required to raise the storage condenser to a potential sufiicient to strike the discharge tube. If it is desired, for example, to determine the occupancy of the outlets over a period of time during which a total of 7200 observations will be made (one hour) the calibrating resistance will be adjusted to raise the storage condenser to the striking potential of the discharge tube responsive to 72 operations of relay J. The tube will then strike 100 times if every observation finds the outlet observed to be occupied, or a proportionately smaller number of times if the occupancy is less. As has already been explained, meter OR counts the number of times the discharge tube strikes and thereby indicates the proper percentage occupancy at the end of the period.

It will now be assumed that three groups of outlets are connected in the same contact position of the access switch. Further, it will be assumed that the first group contains 1 outlet, the second group 4 outlets and the third group 2 outlets. Let these outlets be distributed as follows: Group 1 connected to the bank of wiper I, group 2 to the banks of wipers 2-5 and group 3 to the banks of wipers 6 and I. When the first outlet is marked in the first bank there is no need to provide a connection over wires Commence" for windings (II) of relays U-ZA oi the relay switching device. When the last outlet of a group is connected to the seventh bank there is no need to provide a connection over wire Finish to winding (I) of relay R. In all other cases connections over the wires Finish and Commence to winding (I) of relay R and the second windings of relays UZA respectively are required.

It will now be assumed that the access switch has been set to the position marked by the key associated with the first group of outlets and that relay '1 has operated. As only one outlet is concerned and that is connected in the bank of wiper l a marking will be applied from earth over lower right hand contacts of key K, upper left hand contacts of the same key and crossconnecting block to winding (I) of relay R. Relay R operates and at its contact T3 short-circuits relay 23, at its contact rl opens the circuit for operating relay U and other relays of the chain, and at its contact 1?! opens the circuit for winding (II) of relay V and for the windings (II) of the later relays. Relay A operates and the interaction of relays B and C commences and the outlet in the first bank is observed. The opernected in the bank of wiper I is under continual A observation and when it has been occupied for a period such that the condenser QD with the battery in series with it reaches the striking potential of the discharge tube, the tube strikes and relay E is operated and a record of 1 is made on the recorder. Lamp ORL lights so long as relay E remains operated.

For the observation of the second group of outlets a different key K appropriate to this group is thrown and since the group commences with the outlet connected to the bank of wiper 2 and finishes with that connected to the bank of wiper 5 markings will be applied follows: earth over the lower right-hand and upper lefthand contacts of key K and cross-connecting block to the front of contact 15; and battery over contact .2223 and over the left-hand contacts of key K and cross-connecting block to winding (II) of relay U. Relay U operates at the same time as does relay A and disconnects wiper l thereby preventing an observation being made of the outlet connected over that wiper. The first observation made is, accordingly, over wiper 2 and this is made during the first operating period of relay C. At contact 252 a circuit is completed operates by means of its winding (II).

over winding (II) of relay V, winding (I) of relay U and relay ZB. Relay V operates and at its contact 112 prepares for the release of relay U which takes place on the first operation of relay C. Winding (II) of relay U is de-energized consequent on the opening of contact 2123. On the subsequent release of relay C relay W operates and during the next operating period of relay C the second outlet is observed over wiper 3. The third and fourth outlets are similarly observed. On the subsequent release of relay C relay Y operates and on the subsequent release of relay X by re-operation of relay C completes a circuit at contact 215 for winding (I) of relay R. This circuit is from earth over key K, cross-connecting block, contacts 115, m5, 205, '05, 11.3 and winding (I) of relay R to battery. Relay R operates and holds temporarily over contacts TI and c3 and winding (I) and by operating its contacts rl and r2 releases all the relays of the relay switching devices. The closure of contacts 2M and 2123 provides an immediate operating circuit for the relay connected to the Commence wire in this case relay U. The outlet connected over wiper 6 cannot be observed as relay Z is unable to operate. As a result of the release of relay Y by relay R, relay R is itself released Wiper 2 is again connected to relay J and another cycle of observations of the outlet group is made.

For the observation of the third group, the two outlets of which are connected over wipers 6 and l, a connection is made by way of the cross-connecting block between the lower lefthand contacts of key K to winding (II) of relay Y so that when the key is thrown and relay T has operated, relay Y is operated in a circuit from battery over contact 2113, key K, crossconnecting block, winding (H) of the relay, contacts 1124, 224, wt, T2, 03, H to earth. Contact yl connects relay J to wiper 6 and on the operation of relays A and B the first outlet is observed. Contact 13 closes and extends earth over the back of contacts c3, 12, 144,124,204, m4, winding (II) of relay Z, winding I of relay Y, contacts 23, cal, relay ZB to battery. Relays Z and ZB operate and the circuit over winding (II) of relay Y is opened at contact zbt but that relay holds over its winding (I) and winding (I) of relay Z is energized consequent on the removal. of the shortcircuit at contact 23. On the first operation of relay C, relay Y releases and wiper 1 is connected to relay J. When relay C releases, relay ZA The second outlet of the group is observed before relay C has re-operated. Relay C on re-operating releases relay Z and relays ZA and ZB release with relay C. Contact 2213 re-closes the circuit for winding (II) of relay Y and the cycle of operations recommences.

To calibrate the apparatus the test jack TJ is plugged to short-circuit its two pairs of springs. The closure of the upper pair brings about the operation of relay A and starts the timing device and the closure of the lower pair operates relay J by means of its winding (II) to simulate full occupancy. The resistance CR is then adjusted until two successive records on the apparatus OR occur in one hundredth of the desired analysing period. The same result may also be produced by the operation of the calibration key CK which is conveniently located adjacent to the device OR and possibly remote from the remainder of the equipment.

If more than '7 outlets are to be observed, an expansion unit such as that shown in Fig. 3 may be employed. The expansion unit itself is shown between the broken lines the apparatus shown below the lower line being in the simple recorder as shown in Fig. 2. The expansion unit is arranged i'or the analysis of 21 outlets and is adapted to be fitted to the arrangementshown in Fig. l. The fitting may be made by jacking in the expansion unit to knife contacts provided in the simple analysing unit, and altering the arrangements of straps. The auxiliary switching relays M'U-MZ may beccnnected in place of the access switch wipers 2-5 or the access switch may, in a particular position, give access to these relays. Winding (I) of relay J is disconnected and contacts l of relays U-Z are connected directly to earth. Contact ii is disconnected observed simultaneously and since the auxiliary switching relays provide for seven successive 'observations a total of 2| observations per cycle is had. Relays GA and GB provide for the adjustment of the charging current during calibration if less than the full'number of three outlets is to be observed in any condition of the auxiliary switching relays.

The charging current for the transfer .condensers flows from battery over calibrating resistances CR2 and series resistances SR2 similar to resistances CR and SR in Fig. 2 and contacts of relays JA, JB and JC. There are three parallel circuits, each containing a resistance CR2, a resistance SR2! and a contact of one of the relays JA, JB, JC and it is arranged that each circuit will pass the same charging current. Contact y'al is incuded in one of the parallel circuits, contact y'bl in another and-contact 7'05 in the third parallel circuit. The three circuits are then commoned and connected to contact 7! of relay J, the discriminating relay of Fig. 2. In the circuits over contacts 1b! and id break contacts of relays GB and GA respectively are connected. Relays GA and GB are connected. by straps. as required direct and over contacts of the relays MU-MZ. If, in any set of three out-. lets which are simultaneously observed there should be one disconnected outlet the corresponding contact will be strapped to relay GA, while if there should be two disconnected outlets in the set the appropriate contactwill be strapped to relay GB.

The operation of the arrangementsshown' in Fig. 3 will now be described in connection, where necessary, with those of Figs. 1 and 2, it being assumed that only M outlets are to be observed simultaneously these being arranged as .four sets of three outlets each and one of two outlets.v It

will further be assumed that the four sets of three outlets are to be observed over the front will therefore be connected to apply battery over.

the Commence wire to winding (11) of relay V. To commence operations the lower springs (which alone are shown in Fig. 3) of jack TJ are short-circuited by the insertion of a plug and relays J and AA are thereupon operated. Relay AA at its contacts cal, c112 and (1&3 connects the three discriminating relays to the contacts I, 2, 3 of relays MUMZ. Relay J closes its contact a! to prepare the condenser charging circuit, this circuit being held open at this time by contacts jal, y'bl, jci. Relay V is operated and earth over contacts at and ti is connected to relay MV. Relay MV operates and at its contacts m'vl, 172122 and 122113 connects the discriminating relays to the first set of outlets to be observed. Relay A is operated either by short-circuiting the upper springs of jack TJ (Fig. 1) by the insertion of a plug or due to relay T having operated in a position of the access switch marked by a key such as K, according to the method of associating the expansion unit with the recording unit employed and inter-action of relays B and C comm nces.

The relay switching device operates in the manner previously described and the first observation is made of the set of contacts connected up by relay MV. If all of these are occupied, relays JA, JB and JC will be operated and a charging current for the transfer condensers will flow over the three parallel resistances CR, and contacts deal, 7?)! and jet and the condensers will be charged to a predetermined extent. If only two of the outlets observed are occupied, only two of the discriminating relays will operate and two thirds of this charging current will fiow while if only one outlet of the set is occupied, only one relay will be operated and one third of the charging current will flow. If none of the outlets of the set is occupied, no charging current will flow as none of the relays JA, JB and .30 will be operated. Observations are then made of the other sets of outlets consequent on the operation of relays MW, MX, MY and M2 and the release of relays MV, MW, MK and MY in the manner already described. The recorddng device is operated due to the potential of the condenser QD in series with that of the battery reaching the striking potential of tube DT as a result of repeated charges given to the transfer condensers.

For calibration of the apparatus test jack TJZ is plugged, thereby operating relays JA, JB and JC by means of their windings (II). This simulates a permanently occupied condition of all the outlets and the timing device is started as before and the resistances CR2 adjusted until two successive records are made during an interval of one hundredth of the analysing period. For the purpose of accurate calibration a strap is connected from contact med to relay so that relays GA and GB are both operated when relay MZ operates. This disables the charging circuit over contacts 9'0! and ii)! and permits the calibration for one third the maximum charging current to be made by means of the resistance connected over contact :iai. If the strap is removed from relay GB and connected to relay GA, only the charging circuit over contact if)! is disabled so that calibration for two thirds the charging current may be made by adjusting the resistance connected in the circuit over contact :icl. Finally the strap is removed altogether and adjustment of the resistance connected in the circuit over contact 'bl is made for the passage of the maximum charging current.

It will be understood that where the number of outlets to be observed is not an exact multiple of 3 the odd one or two will always be connected up in the position corresponding to relay MZ operated, so that the proper operation of relays GA and GB is brought about by suitable strapping from contact me l. The other adjustments to cater for the number required are made by suitable strappings to the Commence and Finish terminals as explained in connection with Fig. l.

I claim:

1. In combination, a group of units, a recording apparatus for integrating the occupancy of said group of units over a given period comprismeans for associating said apparatus with each of said units in turn at predetermined in tervals, means for recycling said associating means to reassociate said apparatus with said units in consecutive order, means operated each time said apparatus is associated with an occupied unit, and means controlled by a predetermined number of such operations for indicating percentage occupancy of the group of units.

2. In combination, a group of units, a recording apparatus for integrating the occupancy of said group of units over a given period comprising, means for associating said apparatus with each of said units in turn at predetermined intervals, means for recycling said associating means to reassociate said apparatus with said units in consecutive order, means operated each time said apparatus is associated with an occupied unit, and means controlled by a predetermined number of such operations in a given elapsed time interval for indicating the percentage occupancy of said group of units.

3. In a recording system for integrating occupancy of a number of units of apparatus over an arbitrary period, a plurality of groups of units, a statistical apparatus comprising, a timing device, a serial switching device. a recording device, controlling means associated therewith for determining the particular group of said groups of units to be observed for occupancy and for simultaneously starting said timing device operating, said timing device controlling said serial device to connect each unit of apparatus in the particular group to be observed in turn at equal intervals and in cycles to said recording device, said recording device controlled each time an occupied unit is connected with whereby a record is made equivalent to a predetermined percentage occupancy of the observed units over the said arbitrary period.

4. In a recording system, a plurality of units of apparatus, a statistical apparatus for observing said units to ascertain the degree of occupancy of the several units as a whole over an arbitrary period comprising, a serial switching device, a timing device, and a recording device, wherein said switching device is controlled by said timing device to connect each of said units repeatedly at regular intervals to said recording device, a condenser in said device adapted to be partially charged each time an occupied unit is encountered and discharged when the potential therein is brought to a predetermined value responsive to the receipt of a number of said partial charges equivalent to a given percentage occupancy, and means in said recording device controlled by the discharging of said condenser for indicating said given percentage occupancy.

5. In a recording system wherein observations are made of the conditions of each of a number of trunk lines to ascertain the degree of busy trunks of the total number of trunks over an arbitrary period, a plurality of trunk lines, a serial switching device, means for controlling said serial switching device to "successively test each trunk in turn at predetermined intervals and in cycles, a plurality of condensers parallelly con-Q 6. In a recording system, a plurality of units of apparatus, a statistical apparatus for observing said units to ascertain the degree of occupancy of the several'units as a whole over an arbitrary period comprising, a serial switching device, a timing device, and arecording device, wherein said serial switching device is controlled by said timing device to connect each of said units in turn and at predetermined intervals to said recording device, a plurality of condensers in said timing device parallelly connected and adapted to be charged each time an occupied unit is connected to said timing device, a reservoir condenser, means for serially connecting and discharging said parallelly connected condenser consequent to the charging thereof into said reservoir condenser, said reservoir condenser adapted to be partially charged each time said condensers are discharged, and means responsive when the potential across said reservoir condenser is brought to a value equivalent to a predetermined percentage occupancy for completing a discharge circuit for said reservoir condenser, and means controlled by said reservoir condenser discharge current for operating said recording device to record said percentage occupancy.

'7. In a system as claimed in claim 6, in which the condenser connections are controlled by said timing device and the discharge circuit for said reservoir condenser includes a. charging battery, a gas discharge tube, and a relay, said relay controlling the operation of said recording device.

8. In a recording system, a plurality of units of apparatus, a statistical apparatus for operating said units to ascertain the degree of occupancy of the several units as a whole over an arbitrary period comprising a serial switching device, a timing device, a recording device, wherein said serial switching device is controlled by said timing device to connect each of said units in turn and at predetermined intervals to said recording device, a plurality of parallelly connected condensers, means responsive each time an occupied unit is encountered for completing a charging circuit for said condensers, a reservoir condenser, means controlled by said timing device for altering the connections of said condensers from parallel connections to serial connections and for discharging the condensers into said reservoir condenser to partially charge said reservoir condenser, said reservoir condenser adapted to receive said partial charges until the potential therein is brought to a value equivalent to a predetermined percentage occupancy, and a discharge circuit for said reservoir condenser including a charging battery, a gas discharge tube, and a relay, said relay operated responsive to the completion of said last mentioned discharge circuit for controlling the operation of said recording device.

9. In a system as claimed in claim 4, a discriminating relay, said serial switching device comprising switching relays operable by pulses delivered by said timing device to connect each of said units in succession to said discriminating relay, said discriminating relay operated each time an occupied unit is connected therewith to control the operation of said recording device.

10. In a system as claimed in claim 4, wherein said serial switching device comprises a plurality of switching relays operable by pulses delivered by said timing device to connect each of said units in turn at intervals and in cycles to said recording device, and means for pro-operating certain switching relays at the commencement of a cycle of operation of said switching relays to observe the condition of occupancy of only certain of said units of apparatus.

11. In a recording system, a plurality of groups of apparatus units, selecting means, a timing device, means for operating said selecting means to select a group of units to be observed, and to start said timing device, a sequence switch and a. recorder, said sequence switch controlled by said timing device to successively connect each of the units of the selected group to the recorder at predetermined intervals for a certain period of time, storage means in the recorder for storing a unit registration each time an observed unit is in a certain condition, and an indicator in the recorder operated to indicate a certain percentage whenever the stored registrations are of a value indicating that said percentage of units were in said certain condition.

12. In a recording system for integrating the occupancy of a number of units of apparatus over an arbitrary period, a plurality of groups of units, selecting means, a serial switching device, a timing device, a recording device, means for simultaneously operating said selecting means to select a group of said units to be observed and starting said timing device, storage means associated with said recorder, said timing device operating to control simultaneously said serial switching means to connect repeatedly with each unit of said group and said storage means to store a unit registration each time a connected unit is in a certain condition, and means permanently associated with said storage means effective when the total number of unit registrations therein corresponds to a condition equivalent to a certain percentage occupancy for controlling said recording device. 7

13. Integrating apparatus for determining the occupancy of a group of units over an arbitraryperiod of time, comprising means for periodically testing each unit throughout said period, means operated each time a tested unit is found to be occupied, the ratio of the number of times said last means is operated during said period to the total number of tests made thereby being a measure of the degree of occupancy of said group, and a device operated by said last means during said period and effective to indicate said ratio as a percentage at the end of said period.

14. Integrating apparatus as claimed in claim 13, wherein said device is operated responsive to every X operations of said last means, X being an integer of such value that at the end of said period said device will have been operated a number of times substantially equal to the product obtained by multiplying said ratio by one hundred.

15. Integrating apparatus as claimed in claim 13, wherein said device is operated responsive to every X operations of said last means, having means for adjusting the value of X in accordance with the length of said arbitrary period so that at the end of said period said device will have been operated a number of times substantially equal to the product obtained by multiplying said ratio for that period by one hundred.

HORACE EDGAR HUMPHRIES. 

